Cell death pathways are central to the interaction between pathogenic mycobacteria and host macrophages. The inhibition of cell death of infected host cells is a well-documented, but poorly understood, action of pathogenic mycobacteria. Mycobacteria may accrue several advantages as a result of delaying or inhibiting macrophage cell death, including preservation of a protected growth environment, engagement of intrinsic microcidal activities in the host cell, and optimal stimulation of protective immunity. The genetic basis for this anti-cell death phenotype has not been fully demonstrated or elucidated. Using a Mycobacterium tuberculosis transposon mutant library, we have screened pro-cell death mutants of M. tuberculosis and were able to find multiple genetic loci that are responsible for inhibiting infection-induced cell death of macrophages. This grant proposes to study several of these genes to examine their correlation to virulence and immunogenicity. Additionally, this study will characterize key genetic components of this important virulence trait of mycobacteria, while providing insight and tools necessary to investigate the details of this complex host-pathogen interaction. Our studies may also provide novel approaches for improving mycobacterial vaccines and identifying new TB drug targets. PUBLIC HEALTH RELEVANCE: We propose to study pro-cell death mycobacterial mutants that may enhance priming of adaptive immunity. The results of the study will be useful for the development of new drug targets and TB vaccine candidates.